THVD1406: Data Rate

Francis Jiang

Expert 4130 points

Part Number: THVD1406
Other Parts Discussed in Thread: THVD1426,

Hi Team,

Whether this device can support 9.6ksps~250ksps application? Considering below spec. Thanks in advance.

BRs,

Francis

23 days ago

+1 Ethan Sempsrott 23 days ago

TI__Mastermind 21972 points

Hi Francis,

I would consult this document which shows the THDV1426 transceiver at lower data rates, and it gives good suggestions: https://www.ti.com/lit/an/slla574/slla574.pdf

Technically, THVD1405 will likely have issues at 9.6kbps since the RS-485 bus will be dominant for long periods of time such that the auto direction feature will kick in. However, this transceiver can support 250,000 Kbps just fine. If they add failsafe resistors (pullup on A/pulldown on B), it might allow them to communicate at lower data rates.

Best,

Ethan

0 Francis Jiang 23 days ago in reply to Ethan Sempsrott

TI__Expert 4130 points

Hi Ethan,

Thanks for your detailed reply.

I have one more quick question here: if 9.6kbps may have some issues needs failsafe resistors, what is the lowest rate that can be normally supported? Thanks.

BRs,

Francis

+1 Ethan Sempsrott 19 days ago in reply to Francis Jiang

TI__Mastermind 21972 points

Hi Francis,

We do not specify a minimum data rate for this device. However, I would recommend a data rate that has dominant times shorter than 8us (which is the typical auto direction time). If you add failsafe resistors to the bus like that app note recommends, you can likely use 125,000kbps.

Best,

Ethan

0 Francis Jiang 18 days ago in reply to Ethan Sempsrott

TI__Expert 4130 points

Hi Ethan,

Whether I can understand that 9.6kbps can also use this device with failsafe resistors solution?

If not, which device is more suitable for such 10~30kbps application and has auto-switch? Thanks in advance.

BRs,

Francis

+1 Ethan Sempsrott 17 days ago in reply to Francis Jiang

TI__Mastermind 21972 points

Hi Francis,

At 9.6Kbps, even failsafe resistors will likely not work. However, the customer can test this on their own if they are desperate.

Currently we only have 2 transceivers with the auto-direction feature: THVD1406 and THVD1426. So there are no other options. 9.6Kbps is quite low for RS-485, the lowest standard speed is ~125Kbps.

Best,

Ethan

0 Francis Jiang 17 days ago in reply to Ethan Sempsrott

TI__Expert 4130 points

Hi Ethan,

You are right, it is due to customer switch from TTL.

BRs,

Francis

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THVD1406: Data Rate